Live debate

24 April 2008

The development of any standard can be expected to promote new understandings. This has certainly been the case with vehicle mounted insulating aerial platforms where the process has increased communication between countries and revealed information that perhaps not everyone had previously understood.

There are a number of bodies creating and updating standards for the design and manufacture of insulated devices. However, the use of the products has perhaps not been impacted greatly by these standards. I don't think that is the case any longer, although how that can be true - when some standards are carefully written to exclude the use of products - needs explanation.

Manufacturing base

A large number of the world's insulating aerials, perhaps the majority, are made in the US. (There are, of course, other manufacturers in Argentina, Canada, Finland, France, Italy, Japan, and perhaps others.) In the US the design, manufacture, maintenance, and use of the devices has been covered by one standard since 1969; the American National Standard Institute's ANSI/SIA A92.2.

Now part of the law of the land in the US, the ANSI A92.2 standard has changed as the state- of-the-art changed and as the atmosphere of litigation became more of a factor in society. Standard A92.2-2001 is the latest edition, but a new version that will likely have significant changes is nearing completion, with the approvals process starting perhaps this year.

It is important to understand that A92.2 calls for manufacturers to inform buyers and users of the capabilities of the device by indicating whether it is insulating or not. If it is, it must be identified as one of three categories; A, B or C (see Box Story). Appendix C of A92.2 details the live-line work applications acceptable for the three categories.

Possible confusion

It is possible that, because of the complication of the matter, there may be confusion in both the international and US utilities communities about the design and appropriate use of insulating aerial devices. The matter has been further complicated in the US because workers sometimes forget or even disregard the need to employ their primary insulation - such as insulating gloves or cover up materials - when ‘live working', resulting in human disasters.

If an operator ignores these requirements and forgets that the aerial device only provides protection from a path to ground through the insulated boom, then disaster can occur if the boom-tip conductive components become energized. Some aerial device manufacturers selling in the US are complicating their products by adding materials with high electrical resistance in the boom tip area. It may be that these measures are being taken because they are sometimes being accused of providing unsafe products, even when the cause of incidents are clearly failures by end users to employ mandatory safety measures.

This writer contends that US manufactured machines are being bought and specified for uses that may not follow the work methods envisioned by the writers of A92.2. As an American, I have a subjective view, but truly believe that US products generally offer the best value and are the safest on the planet. I would hasten to add that it is extremely important that the selected methods and the aerial device employed for the work to be performed are vital to the safety of the user(s).

Work on live lines has been done in various parts of the world for many decades. It began in the US during the late 1930s and gained widespread popularity after World War II. The work was mostly accomplished using ‘hot sticks' or insulating gloves. The ‘bare hand' technique only began in the US, I believe, on lines where voltage levels were too high for ‘gloving' methods, where ‘hot sticking' was considered too cumbersome, and where the distances between conductors were great enough that ‘bare hand' methods could be employed with a satisfactory degree of safety.

I understand that across the Atlantic, particularly in France where electrical circuits are generally less congested, ‘bare hand' methods have been used for many years on lines of less voltage levels (distribution levels of 20kV phase to phase are, I understand, frequently worked ‘bare hand' by EDF). The insulating devices used for this work will naturally need all conductive components at the boom tip bonded together to prevent the occurrences mentioned earlier here. If a device built to ANSI A92.2 Category C (or B) was used for ‘bare hand' work in the US or Europe there might be dangerous results. On the other hand, an insulating device suitable for ‘bare hand' work (e.g., a Category A device) might result in trouble if used where a machine without bonded components would be expected.

Standards dilemma

You can now see a dilemma in attempting to draft an International standard that takes into account the differences of how work is accomplished. Also, remember we have not discussed how work is accomplished in Japan or other areas of the world.

In 1991 the International Electrotechnical Commission (IEC) published TC-1057, an International Standard for Insulating Aerials. I think it badly needs updating as I am not aware of anyone using all its criteria for the design and manufacture of insulating aerial devices.

IEC Technical Committee TC-78 (Work Group 12) formed a project team that is attempting to work out the varying requirements for manufacture of insulating aerial devices. Under IEC rules the team has to produce a document that does not dictate any work practices or methods. I would describe this as ‘a tall order' and yet the standard - to be called IEC 61057 - is nearing completion of the drafting process.

IEC 61057 has dealt with the complication of component selection, and the Category approach of the ANSI A92.2 standard, by simply listing the various options and placing the onus of proper selection in the hands of the purchaser. A thorough understanding of the work to be accomplished, the method(s) to be employed, and the purpose of all the components of the insulating aerial device, is necessary to procure a device that can be used safely.

In my view that is another ‘tall order'. Not all the live working in the world is carried out by large electric utilities with a capable staff of experts that may be needed to correctly configure an insulating aerial from a list of potential components.

It is necessary to have a list of components arranged so as not to break the sacred IEC rule, that of not dictating a particular work practice. I am encouraged, however, that a significant effort is being made to produce annexes to the standard providing information about the various work methods and the appropriate precautions for each. I expect that the IEC 61057 final draft process will near completion in 2006.

When the IEC document is completed and the International community deliberates their approval, I encourage you to express your thoughts to your national representatives.

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